1. Field of the Invention
The present invention relates to a sheet conveying apparatus with which simplification of apparatus expansion operations and reduction of the apparatus costs can be realized and to an image forming apparatus provided therewith.
2. Related Background Art
With the diversification of users"" needs, the image forming apparatus in recent years have come to be configured in such a manner that some processing apparatus for performing processing on a variety of functions and sheets of the image forming apparatus can be added thereto according to the request of the users. One of the concrete examples of these apparatus is disclosed in Japanese Patent Application Laid-Open No. 8-48447 (refer to FIGS. 12A and 12B).
As is disclosed in the specification, in a printer 100 as an image forming apparatus, a sheet discharge portion including sheet discharge rollers 300 is formed as a unit and a sheet discharge roller unit 200 is replaced with a predetermined unit (for example, an option unit 400 shown in FIG. 12B) at the time of performing a desired processing such as double side conveyance and face-up sheet discharge, thereby the mechanism of the printer body can be simplified. Further, in regard to the printer body 100 as an image forming apparatus, a small-size printing apparatus body can be configured only by providing means for image formation and for sheet feeding; accordingly, for the uses requiring a basic mechanism alone, a costless apparatus without any extra equipment can be provided.
This means that a system which answers the users"" need for performing a certain process can be proposed just by fitting an apparatus for performing a predetermined processing to an apparatus for simply forming images on a sheet.
The image forming apparatus as described above, however, gives rise to problems described below.
In cases where the sheet discharge roller unit 200, which has an ordinary configuration, is replaced by the option unit 400 having sheet roller pairs 300, 350 as shown in FIG. 12B (the sheet discharge roller pair 300 is not shown in the drawing), the sheet discharge roller pair 300 existing in the sheet discharge roller unit 200 is to be replaced together. The sheet discharge roller pair 300 itself is necessary for the option unit 400 and its function to convey sheets is the same even in the sheet discharge roller unit 200.
In the configuration of the image forming apparatus of the prior art, when the user intends to alter the apparatus by adding any desired system thereto, the parts, such as sheet discharge roller pair 300, which do not need to be replaced have to be replaced together with the unit. The cost of the units replaced includes that of the parts which do not have to be replaced in themselves; accordingly, it becomes higher unnecessarily. Thus, the users desiring to alter the system of their apparatus have had to pay for it.
The present invention is to provide an image forming apparatus which is configured in such a manner that, when its system needs to be altered, the functions needed to be altered alone can be added to/replaced with the original ones, thereby the cost of altering the system can be held down and the alteration of the same can be simplified. The configuration includes a rotor to which torque in the fixed direction is transmitted and transmitting means for transmitting torque to the rotor, and the transmitting means is replaceable with second driving means capable of freely rotating the rotor in both the forward and the backward directions.